Here, four startups with the capital and ambition to remake U.S. health care. May the odds be in their favor.

Eager to leap in where so many others have stumbled, Silicon Valley investors have been pumping capital—$1.2 billion in 2015 alone—into startups taking on the task of improving health insurance for individuals and employers. It’s not for the faint-hearted: The industry is rapidly consolidating, making it harder for new companies to gain traction. But the payoff could be huge. “It’s a big, juicy opportunity with a lot of market cap,” says Sequoia Capital’s Mike Dixon. Here, four of the biggest bets on the future of health insurance.